A duplicate project was jointly planned by U.S. and U.S.S.R. scientists to study the effects of microwave radiation on the nervous system. The purpose of the duplicate project was to compare experimental methodologies and to determine response indicators which would be sensitive to exposure to microwave radiation. Fischer-344 rats were exposed for 7 hours for one day to 2.45-GHz microwave radiation at an incident power density of 10 mW/cm2 after eight days of adaptation to the exposure cages and EEG connections. EEG measurements before, during and after exposure were made and light evoke potential measurements were also recorded before and after exposure. The behavioral test used to evaluate changes were passive avoidance to foot shock and activity in an open field. Biochemical measurements were made immediately after exposure in the rat cerebral cortex. Na+K+-ATPase, Mg2+-ATPase, Mg2+Ca2-ATPase activities and alkaline phosphatase were measured. Results of the EEGs showed a shift in frequencies at various times during the exposure period. The shifts were in the direction of a greater percentage of the spectrum being in the lower frequencies of the EEG. The exposed and control animals did not respond differently to the light evoke stimulation of the cortex. No differences were observed in the passive avoidance response and open field activity. The data from the biochemical measurements showed that Na+K+-ATPase was the only biochemical parameter significantly changed by the exposure. A lower Na+K+-ATPase activity was observed in the synaptosomes of the cortex in the exposed animals.